Investigation of solubility and diffusion of oxygen in refractory metals Second quarterly report, 1 Oct. - 31 Dec. 1965
Electric resistivity measurements to determine solubility and diffusion of oxygen in tantalum, columbium, and alloys
NIOBIUM↗
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Design of Silicide-Strengthened Nb–Si–Cr–(Mo) alloys for additive manufacturing
Three high–intermetallic volume Nb–Si–Cr–(Mo) alloys were designed using CALPHAD modeling with the goal of identifying high–specific strength, oxidation-resistant alloys that can be additively manufactured using powder bed fusion. The silicides Nb 5 Si 3 and Nb 9 Si 2 Cr3 were targeted as the primary strengthening phases, and the addition of Cr promoted the NbCr 2 phase. These alloys were cast and surface-processed with electron beam welding at different speeds to simulate additive manufacturing, and the phases and microstructures of both cast and welded regions were characterized. The weld processing was found to produce fine-grained microstructures in each alloy with fine-scale intermetallics uniformly distributed among a body-centered cubic Nb matrix. Microstructural refinement and hardness were found to increase with weld velocity; one alloy reached its highest hardness of approximately 16 GPa before the brittleness at higher velocities became detrimental. One alloy was found to be qualitatively the least brittle while also attaining a hardness of 13 GPa and was therefore identified as a good candidate for additive manufacturing.
36 MATERIALS SCIENCE↗
The measurement of heats of solution of high melting metallic systems in an electromagnetic levitation field
A method was tested for measuring the enthalpies of mixing of liquid metallic alloying systems, involving the combination of two samples in the electromagnetic field of an induction coil. The heat of solution is calculated from the pyrometrically measured temperature effect, the heat capacity of the alloy, and the heat content of the added sample. The usefulness of the method was tested experimentally with iron-copper and niobium-silicon systems. This method should be especially applicable to high-melting alloys, for which conventional measurements have failed.
Frohberg, M. G.↗
Analysis of the Surface Morphology and Chemical Composition of Zr-Nb3Sn Alloys with Zr Different Concentrations
The inclusion of zirconium (Zr) in niobium-tin (Nb3Sn) significantly enhances the performance of Nb3Sn radiofrequency cavities in high magnetic fields. This research project is dedicated to characterizing the surface properties and chemical composition of Zr-doped Nb3Sn. Two different concentrations of Zr were used for doping: approximately 0.5% and 24%. Various spectroscopy techniques were employed to analyze how the surface morphology and chemical composition of Nb3Sn change with increasing Zr content. The findings of this study indicate that the grain size decreases as the Zr concentration increases. In samples with 24% Zr, nanometer-sized particles, likely oxides, were observed. X-ray photoelectron spectroscopy (XPS) data revealed that the thickness of niobium oxides (NbOx) decreases with increasing Zr, while the thickness of tin oxides (SnOx) increases. Additionally, grain size distribution analysis showed that the average grain size is around 5300 nm , with a grain area density of about 165 grains/μm .
Sue, Micah↗
Compatibility of tantalum, columbium, and their alloys with hydrogen in presence of temperature gradient
Compatibility of tantalum and niobium with hydrogen in presence of temperature gradient
NIOBIUM↗
Containerless undercooling and solidification in drop tubes
A containerless low-gravity environment, produced within a 32 m drop tube apparatus, has been used to undercool and solidify metals, alloys or glasses by eliminating crucible induced nucleation processes. Niobium droplets with diameters in the range of 2 to 5 mm have been undercooled by 525 K which corresponds to the maximum undercooling reported by Turnbull and others on fine dispersions of low melting point metals. Solidification at large undercooling resulted in single crystalline spheres with the formation of interdendritic shrinkage channels on the sample surface rather than interior shrinkage cavities. The grain refinement as observed for Ni samples undercooled and solidified in fused silica crucibles does not occur in free-falling drops of Nb. A calculated solidification speed of undercooled Nb is compared to Ni. A solidification speed of 320 m/s is found for the Nb drops. This solidification speed is greater than or comparable to the solidification speeds calculated in splat cooled samples. Thus, a drop tube apparatus can be useful in the preparation and study of high temperature metastable compounds or alloys in bulk form.
Lacy, L. L.↗
Synthesis and Characterization of Superconductor Diodes
In the era of modern computing, quantum bits (or qubits) are extensively researched due to their ability to perform computations exponentially faster than classical computers. One promising method for synthesizing qubits on a macroscopic scale is through superconductor diodes (SDs). Unfortunately, SDs are currently limited by their dependence on extremely low temperatures (T ≈ 0K), which restricts their practical usability at larger scales. To address this limitation, researchers are exploring new materials and methods to identify superconductors with higher critical temperatures. My research at the Lawrence Livermore National Laboratory (LLNL) focuses on synthesizing and characterizing superconductor diodes to determine their efficiency for quantum computing applications. Bismuth thin films were synthesized with magnetron sputtering with separate thicknesses which provides information on methods to alter their resistivity. Bismuth was characterized as the topological insulator used in the diode, and its resistivity was measured using a standard four-point probe technique with 1 mA current. Bismuth (99.99% pure) was then purified in a tubular furnace at 400C to use within a Josephson junction as a topological insulator. Niobium and Tantalum Josephson junctions were then synthesized, and they were characterized using a lock-in amplifier four-point probe technique. Materials such as niobium and tantalum are used in high-entropy alloy research, which is a relatively new class of material that has little research within the superconductor diode community, yet the current research shows promise. We anticipate that testing high-entropy superconductors will reveal crucial factors, potentially leading to the development of high-temperature superconductors in the future.
36 MATERIALS SCIENCE↗
Microstructures in rapidly solidified niobium aluminides
The microstructures of niobium aluminides produced by chill block melt spinning were compared to those of niobium aluminides produced by conventional casting. The rapidly solidified alloys were rapidly solidified by melt spinning in an argon atmosphere, and the melt-spun ribbons were examined by optical, X-ray, and TEM techniques. Microstructures were found to range from single-phase for Nb-75 at. pct Al (NbAl3) to two phase for Nb-46 at. pct Al (NbAl3 + Nb2Al). It was found that the melt spinning of Nb-aluminides produced finer grained microstructures than those produced in induction-melted ingots or in powders produced by the rotating electrode process. Ternary additions such as Cr, Ti, and Si tended to form intermetallic phases along the grain boundaries.
Hebsur, Mohan G.↗
Solidification cracking of refractory alloys: a computational and machine learning study to investigate composition-dependence for improved weldability and additive manufacturability
Large-batch numerical, CALculation of PHAse Diagrams (CALPHAD)-based solidification cracking calculations are performed and then analyzed with machine learning methods to generate models that relate chemistry of refractory alloys to cracking susceptibility. Kou’s solidification cracking index is used to study the refractory alloys including O, N, C binary mixtures with Mo, Ta, Nb, and W, the molybdenum-based TZM, Niobium-based C103, and Tantalum-based T111 and Ta-10 W, as well as hypothetical refractory ternary alloys. Findings strongly validate Kou’s Crack Susceptibility Index (CSI) against Varestraint test data for Nb- and Ta-based alloys, establishing CSI thresholds where refractory alloys with CSI < 15,000 K are likely weldable, CSI > 15,000 K are prone to cracking, and CSI > 25,000 K are likely unweldable (or unprintable). Furthermore, interstitial elements C, N, and O significantly increase crack susceptibility, with some existing material specifications coinciding with peak cracking susceptibility concentrations. Finally, machine learning-derived elemental potency factors enable rapid prediction of CSI from alloy chemistry for C103, TZM, Ta-10 W, and T-111 alloys. These results provide practical guidance for feedstock selection, powder reuse limits, and alloy specification amendments for welding and additive manufacturing applications.
36 MATERIALS SCIENCE↗
Applications of containerless processing in the studies of metals and alloys
The use of containerless processing in nucleation and microstructural studies of alloys is reviewed in terms of approaches and recent results. Drop-tube studies of niobium based on a statistical approach are discussed, and experiments are described which permit the study of the solidification front across the surface of a specimen. The various alloys studied are reviewed in terms of facilitated observations of metastability, chemical homogeneity, and microstructural refinement. Heterogeneous nucleation is reported for a preexponential factor of 10 exp 27 and a critical free energy of 46-56kT. The theoretical relationship between undercooling and solidification velocity correlates with containerless test observations at large solute concentrations. Containerless processing is effective for studying the properties of liquid metals or accessing the metastable thermodynamic regime.
Bayuzick, R. J.↗
Determination of hydrogen permeability in commercial and modified superalloys
The results of hydrogen permeability measurements on several iron- and cobalt-base alloys as well as on two long-ranged ordered alloys over the range of 705 to 870 C (1300 to 1600 F) are summarized. The test alloys included wrought alloys N-155, IN 800, A-286, 19-9DL, and 19-9DL modifications with aluminum, niobium, and misch metal. In addition, XF-818, CRM-6D, SA-F11, and HS-31 were evaluated. Two wrought long-range ordered alloys, Ni3Al and (Fe,Ni)3(V,Al) were also evaluated. All tests were conducted at 20.7 MPa pressure in either pure and/or 1% CO2-doped H2 for test periods as long as 133 h. Detailed analyses were conducted to determine the relative permeability rankings of these alloys and the effect of doping, exit surface oxidation, specimen design variations, and test duration on permeability coefficient, and permeation activation energies were determined. The two long-range ordered alloys had the lowest permeability coefficients in pure H2 when compared with the eight commercial alloys and their modifications. With CO2 doping, significant decrease in permeability was observed in commercial alloys--no doped tests were conducted with the long-range ordered alloys.
Bhattacharyya, S.↗
Conductivity of GRCop-42 Alloy Enhanced
GRCop-84, a material developed at the NASA Glenn Research Center, has shown considerable promise for staged combustion rocket engine cycles such as the Space Shuttle Main Engine. However, for an expander cycle rocket engine, the transfer of heat to the fuel is a paramount factor in determining the efficiency of the engine. Examples of current and potential future expander cycle rocket engines are the Pratt & Whitney RL-10, RL-60, and RLX engines. Development of a higher conductivity version of GRCop-84 was undertaken to meet these needs. All expander cycle engines need a main combustion chamber liner with the maximum possible thermal conductivity. In an effort at Glenn to trade some of the greatly increased mechanical properties of GRCop-84 for improved thermal conductivity, the amounts of chromium and niobium were halved. The new Cu-4 at.% Cr-2 at.% Nb alloy was designated GRCop-42.
Ellis, David L.↗
Superalloy resources: Supply and availability
Over the past several decades there have been shortages of strategic materials because of our near total import dependence on such metals as chromium, cobalt, and tantalum. In response to the continued vulnerability of U.S. superalloy producers to disruptions in resource supplies, NASA has undertaken a program to address alternatives to the super-alloys containing significant quantities of the strategic materials such as chromium, cobalt, niobium, and tantalum. The research program called Conservation of Strategic Aerospace Materials (COSAM) focuses on substitution, processing, and alternate materials to achieve its goals. In addition to NASA Lewis Research Center, universities and industry play an important role in the COSAM Program. This paper defines what is meant by strategic materials in the aerospace community, presents a strategic materials index, and reviews the resource supply and availability picture from the U.S. point of view. In addition, research results from the COSAM Program are highlighted and future directions for the use of low strategic material alloys or alternate materials are discussed.
Stephens, Joseph R.↗
Resources - Supply and availability
Over the past several decades there have been shortage of strategic materials because of our near total import dependence on such metals as chromium, cobalt, and tantalum. In response to the continued vulnerability of U.S. superalloy producers to disruptions in resource supplies, NASA has undertaken a program to address alternatives to the super-alloys containing significant quantities of the strategic materials such as chromium, cobalt, niobium, and tantalum. The research program called Conservation of Strategic Aerospace Materials (COSAM) focuses on substitution, processing, and alternate materials to achieve its goals. In addition to NASA Lewis Research Center, universities and industry play an important role in the COSAM Program. This paper defines what is meant by strategic materials in the aerospace community, presents a strategic materials index, and reviews the resource supply and availability picture from the U.S. point of view. In addition, research results from the COSAM Program are highlighted and future directions for the use of low strategic material alloys or alternate materials are discussed.
Stephens, Joseph R.↗
High-$Q_0$ treatment of CEBAF 1.5 GHz SRF cavities
The Continuous Electron Beam Accelerator Facility (CEBAF) was the first large-scale accelerator to employ superconducting radiofrequency (SRF) cavities for continuous-wave operation. Ongoing research and development efforts continue to focus on increasing the intrinsic quality factor (Q 0 ) of these cavities in order to reduce cryogenic losses while maintaining operational gradients. Here, in this work, we report on the application of high-Q 0 surface treatments to single-cell and multicell C100 and C75 style 1.5 GHz niobium cavities used in the CEBAF accelerator. Nitrogen infusion and oxygen alloying via medium-temperature baking were applied under heat-treatment constraints relevant to existing cavity hardware. Both processes yielded substantial improvements in Q 0 at moderate accelerating gradients, achieving values of approximately 2 × 10 10 at 2.07 K and 20 MV/m. The effectiveness of nitrogen infusion at reduced annealing temperatures and the successful extension of oxygen alloying to multicell cavities are demonstrated. These results establish viable pathways for implementing high-Q 0 treatments in CEBAF-compatible cavities and support future integration into cryomodules for reduced operational cryogenic load.
Dhakal, Pashupati [Thomas Jefferson National Accel↗
Salt‐Assisted Vapor–Liquid–Solid Growth of 1D van der Waals Materials
The method of salt-assisted vapor–liquid–solid (VLS) growth is introduced to synthesize 1D nanostructures of trichalcogenide van der Waals (vdW) materials, exemplified by niobium trisulfide (NbS 3 ). The method uses a unique catalyst consisting of an alloy of Au and an alkali metal halide (NaCl) to enable rapid and directional growth. High yields of two types of NbS 3 1D nanostructures, nanowires and nanoribbons, each with sub-ten nanometer diameter, tens of micrometers length, and distinct 1D morphology and growth orientation are demonstrated. Strategies to control the location, size, and morphology of growth, and extend the growth method to synthesize other transition metal trichalcogenides, NbSe 3 and TiS 3 , as nanowires are demonstrated. Finally, the role of the Au–NaCl alloy catalyst in guiding VLS synthesis is described and the growth mechanism based on the relationships measured between structure (growth orientation, morphology, and dimensions) and growth conditions (catalyst volume and growth time) is discussed. These results introduce opportunities to expand the library of emerging 1D vdW materials to make use of their unique properties through controlled growth at nanoscale dimensions.
1D van der Waals material↗
Containerless high temperature property measurements
Containerless processing in the low gravity environment of space provides the opportunity to increase the temperature at which well controlled processing of and property measurements on materials is possible. This project was directed towards advancing containerless processing and property measurement techniques for application to materials research at high temperatures in space. Containerless high temperature material property studies include measurements of the vapor pressure, melting temperature, optical properties, and spectral emissivities of solid boron. The reaction of boron with nitrogen was also studied by laser polarimetric measurement of boron nitride film growth. The optical properties and spectral emissivities were measured for solid and liquid silicon, niobium, and zirconium; liquid aluminum and titanium; and liquid Ti-Al alloys of 5 to 60 atomic pct. titanium. Alternative means for noncontact temperature measurement in the absence of material emissivity data were evaluated. Also, the application of laser induced fluorescence for component activity measurements in electromagnetic levitated liquids was studied, along with the feasibility of a hybrid aerodynamic electromagnetic levitation technique.
Nordine, Paul C.↗
High-throughput oxidation screening and down-selection of refractory high entropy alloys in the Al-Cr-Mo-Nb-Ta-Ti system
Rapid experimentation and characterization are ever-present needs in the discovery of high entropy alloys. High entropy alloy systems are difficult to survey with systematic composition sweeps using traditional synthesis methods. The number of distinct compositions in even a four-element system is experimentally intractable. Exploration of these, and higher-element systems, necessitates thermodynamic prediction coupled with an automated sample creation method and a rapid screening methodology to effectively down-select alloys with targeted properties. As a result, a high-throughput method for evaluating the oxidation performance of refractory high entropy alloys was developed and tested. The six-element system of aluminum, chromium, molybdenum, niobium, tantalum, and titanium was evaluated for single phase stability and short-duration oxidation resistance. Target compositions were initially determined via thermodynamic predictions of single-phase stability across a wide temperature range. A twenty-five-sample build plate was produced using directed energy deposition additive manufacturing. After fabrication, the twenty-five 1 cm 3 samples were heat treated and characterized for composition and phase identification. The build plate was exposed to a high temperature oxidizing environment at 1000 °C for three hours. After oxidation, the composition, morphology, and chemistry of the oxides formed were characterized. Of the twenty-five samples produced, nine exhibited a favorable oxidation response, from which a single-phase BCC alloy at a composition of Al 13 Cr 7 Mo 19 Nb 18 Ta 26 Ti 17 was identified as the alloy with the most protective oxidation coating with a thin, adherent oxide scale. Finally, the complete experimental down-selection—from machine setup to final alloy identification—required approximately 45 labor hours, demonstrating a rapid validation for alloy discovery.
Additive manufacturing↗